The invention relates to an optoelectronic semiconductor device with an optoelectronic element comprising a semiconductor body with a semiconductor substrate and a superimposed, substantially plane semiconductor layer structure of III-V semiconductor materials, a mesa being formed at a surface of the semiconductor body by means of selective deposition and forming part of the optoelectronic element. The invention also relates to a method of manufacturing an optoelectronic semiconductor device comprising an optoelectronic element.
Such semiconductor devices are widely used in optical telecommunication, optical disc systems, etc. The optical element often is a semiconductor diode laser or LED, but it may alternatively comprise, for example, a (passive) radiation guide or photodiode. They often include mesas which have a comparatively small dimension in at least one direction substantially perpendicular to the direction of the semiconductor layer structure, for example, strip-shaped mesas having a width of approximately 1 to 10 .mu.m.
Such an optoelectronic semiconductor device is known from European Patent 0 182 903 (date of publication 09-08-1989). The known semiconductor device comprises as the optoelectronic element a semiconductor diode laser of the so-called ridge waveguide type, in which the semiconductor layer structure comprises an active layer situated between two cladding layers which form a pn junction, on which active layer is provided an insulating layer in which a strip-shaped opening is present in which a mesa is formed by means of selective deposition. Over the mesa and the insulating layer is a metal layer which forms one of the connection conductors of the diode laser of which the mesa forms part. The other connection conductor is at the lower side of the substrate. Such a semiconductor device has many and important advantages, such as a simple manufacture, simple contacting, and low contact resistance.
A disadvantage of the known semiconductor device is that the deposition is not as selective as is desired, and that often parasitic polycrystalline material is formed during manufacture next to the mesa to be formed on an insulating layer which acts as a mask for the selective position. The parasitic deposition is undesirable since it is comparatively rough. Another disadvantage of the known device is, as has been shown in practice, that during cleaving thereof unevennesses are often formed on the cleavage surface, e.g. so-called cleavage steps, in the vicinity of, often just below the mesa, which is particularly undesirable since the optoelectronic element is situated at the area of the mesa. Another disadvantage of the known device was found to be that the height of the mesa is less easily adjustable. Moreover, the mesa has near its edges sometimes a considerable thickening, so that the mesa is rough, which forms a problem inter alia during the provision of a thin metal layer over the mesa which is to act as a connection conductor.